title: Role of the methylcitrate cycle in growth, antagonism and induction of systemic defence responses in the fungal biocontrol agent Trichoderma atroviride.
abstract: Methylisocitrate lyase (MCL), a signature enzyme of the methylcitrate cycle, which cleaves methylisocitrate to pyruvate and succinate, is required for propionate metabolism, for secondary metabolite production and for virulence in bacteria and fungi. Here we investigate the role of the methylcitrate cycle by generating an mcl deletion mutant in the fungal biocontrol agent Trichoderma atroviride. Gene expression analysis shows that a basal expression of mcl is observed in all growth conditions tested. Phenotypic analysis of an mcl deletion mutant suggests the requirement of MCL in propionate resistance, growth, conidial pigmentation and germination, and abiotic stress tolerance. A plate confrontation assay did not show a difference between the WT and the Δmcl strain in antagonism towards Botrytis cinerea. However, the Δmcl strain displays reduced antagonism towards B. cinerea based on a secretion assay. Furthermore, an in vitro root colonization assay shows that the Δmcl strain had reduced ability to colonize Arabidopsis thaliana roots, which results in reduced induction of systemic resistance towards B. cinerea. These data show that MCL is important not only for growth and development in T. atroviride but also in antagonism, root colonization and induction of defence responses in plants.
authors.affiliation: Uppsala BioCenter, Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences, Box 7026, 75007 Uppsala, Sweden.
authors.forename: Mukesh K
authors.initials: MK
authors.lastname: Dubey
authors.affiliation: Uppsala BioCenter, Department of Chemistry, Swedish University of Agricultural Sciences, Box 7015, 75007 Uppsala, Sweden.
authors.forename: Anders
authors.initials: A
authors.lastname: Broberg
authors.affiliation: Uppsala BioCenter, Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences, Box 7026, 75007 Uppsala, Sweden.
authors.forename: Dan Funck
authors.initials: DF
authors.lastname: Jensen
authors.affiliation: Uppsala BioCenter, Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences, Box 7026, 75007 Uppsala, Sweden.
authors.forename: Magnus
authors.initials: M
authors.lastname: Karlsson
mesh_terms: D000898:Antibiosis; D017360:Arabidopsis / Q000382:microbiology; D020171:Botrytis / Q000254:growth & development; D019755:Carbon-Carbon Lyases / Q000235:genetics / Q000378:metabolism*; D002951:Citrates / Q000378:metabolism*; D017353:Gene Deletion; D020869:Gene Expression Profiling; D056265:Microbial Interactions; D018517:Plant Roots / Q000382:microbiology; D014242:Trichoderma / Q000201:enzymology / Q000254:growth & development* / Q000378:metabolism* / Q000502:physiology
chemical_list: D002951:Citrates; C031605:2-methylcitric acid; D019755:Carbon-Carbon Lyases; C417277:methylisocitrate lyase